It is known to use overhead rail systems along which trolleys travel in order to move goods during processing or manufacture. The systems are used for transporting various types of merchandise, including hanging meat, garments and other products, through manufacturing, warehousing and distribution facilities. One typical overhead conveyer system pushes heavy, metal trolleys along a track system. The trolleys carry loads of products. The overhead rail systems are designed and installed so that goods may be suspended from the trolleys and then moved in different directions along the rail system to transfer the goods from a first location to a second location. Some such systems employ a system of two, parallel tracks or rails; an upper power rail and a lower free rail. The upper rail generally includes a drive chain that engages a component of the trolley, while the trolley's wheels are designed to ride within the free rail. The load supported by the trolley is most often suspended below the level of the free rail.
Oftentimes, overhead rail systems use a rail switching mechanism at points in the track or rail where rails traveling in different directions intersect. The switching mechanism operates to control and direct the movement of the trolleys along various routes of the track system, such as to introduce a turn onto a different rail.
One form of switching mechanism is a gear switch. Current gear switches are typically formed of an assembly including two gear assemblies, each of which are operable to move gates into and out of engagement with a rail section connected thereto. The two gear assemblies in current switching mechanisms are arranged such that they are horizontally spaced apart in a plane which is perpendicular to the rail and at a height which is approximately parallel to each other and the rail. More specifically, the pivot axis of each of the gear assemblies is level and positioned in the same plane.
In a common conveyor assembly using a gear switch mechanism, a power chain is run through a bridge which is often used to connect first and second rail sections forming a portion of the rail switch assembly. In conveyors, projections, often referred to as pusher dogs, are suspended from the drive chain. A pusher dog assembly may be provided for the transportation of products on trolley in a conveyer system. A pusher dog is, generally, a projection that engages and pushes loads along a track or conveyor system. Thus, a power chain or drive chain pusher dog may be engaged to the chain and may be designed to directly engage trolley and push them along the series of interconnected rails. Movement of the trolley is thus accomplished by the mechanized action of the pusher dog on a protruding trolley part. Therefore, the drive chain commonly includes a pusher dog that extends downward from the drive chain and engages a part of the trolley that protrudes above the level of the free track or rail.
Unfortunately, current switching mechanisms, due to the travel path and location of the gear assemblies carrying the gate members, are prone to catch or bind with the pusher dog if the gate is switched at the wrong time. Thus, a high level of precision and timing must be used to switch the rail, or the drive chain must be stopped.
Additionally, in current switching mechanisms, a trolley stop is used to prevent overrun or interference of a trolley with a rail that is not currently being used. A current trolley stop used with such switch mechanisms is formed by a piece or member that is connected on the side of the rail section by a pivot member. At the lower end of the trolley stop is a weight, which causes rotation about the pivot member. Unfortunately, due to the side attachment of the trolley stop to the rail, and the position of the weight, these trolley stops are prone to bind. Moreover, the gate member must be precisely closed, coming over the top of the mechanism, or the gate may become wedged in place in the gate receptor, inhibiting the switching of the rails.
Accordingly, what is needed in the art is a rail switching mechanism that can be switched without binding. There is also a need in the art for a trolley stop for such a switch mechanism that may pivot on center or near center with the rail to stop the trolley or engage the switching mechanism.